Method for depositing a chlorine-free conformal sin film

ABSTRACT

Described are methods of making silicon nitride (SiN) materials on substrates. Improved SiN films made by the methods are also included. One aspect relates to depositing chlorine (Cl)-free conformal SiN films. In some embodiments, the SiN films are Cl-free and carbon (C)-free. Another aspect relates to methods of tuning the stress and/or wet etch rate of conformal SiN films. Another aspect relates to low-temperature methods of depositing high quality conformal SiN films. In some embodiments, the methods involve using trisilylamine (TSA) as a silicon-containing precursor.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 14/065,334, filed Oct. 28, 2013, titled “METHOD FORDEPOSITING A CHLORINE-FREE CONFORMAL SiN FILM,” which is a continuationof U.S. patent application Ser. No. 13/414,619 (now U.S. Pat. No.8,592,328), filed Mar. 7, 2012, titled “METHOD FOR DEPOSITING ACHLORINE-FREE CONFORMAL SiN FILM,” which claims priority to U.S.Provisional Application No. 61/588,964 filed Jan. 20, 2012, all of whichare incorporated by reference herein in their entireties for allpurposes.

INTRODUCTION

1. Field

The present disclosure relates generally to formation of SiN materialson substrates. More particularly, the disclosure relates to formation ofSiN films on semiconductor substrates.

2. Background

Silicon nitride (SiN) thin films have unique physical, chemical andmechanical properties and thus are used in a variety of applications,particularly semiconductor devices, for example in diffusion barriers,gate insulators, sidewall spacers, encapsulation layers, strained filmsin transistors, and the like. One issue with SiN films is the relativelyhigh temperatures used to form the films, for example, in Front End ofLine (FEOL) applications, SiN films are typically deposited by chemicalvapor deposition (CVD) in a reactor at greater than 750° C. usingdichlorosilane and ammonia. However, as SiN films are used in late-stagesemiconductor fabrication processes, and as device dimensions continueto shrink, there is an increasing demand for SiN films to be formed atlower temperatures, for example less than 600° C.

SUMMARY

Described are methods of making silicon nitride (SiN) materials onsubstrates. Improved SiN films made by the methods are also included.One aspect relates to depositing chlorine (Cl)-free conformal SiN films.In some embodiments, the SiN films are Cl-free and carbon (C)-free.Another aspect relates to methods of tuning the stress and/or wet etchrate of conformal SiN films. Another aspect relates to low-temperaturemethods of depositing high quality conformal SiN films. In someembodiments, the methods involve using trisilylamine (TSA) as asilicon-containing precursor.

One aspect is a method that includes periodically exposing the substrateto a vapor phase flow of a halogen-free silicon-containing reactantwherein the halogen-free silicon containing reactant is adsorbed ontothe surface of the substrate, exposing the substrate to a vapor phaseflow of a first nitrogen-containing reactant wherein thenitrogen-containing reactant is adsorbed onto the surface of thesubstrate, and periodically igniting a plasma in the reaction chamberwhen vapor phase nitrogen-containing reactant is present in the reactionchamber and the vapor phase flow of the halogen-free silicon-containingreactant has ceased. In some embodiments, the halogen-free siliconcontaining reactant is TSA. In certain embodiments, the firstnitrogen-containing reactant is carbon-free. Examples of carbon-freenitrogen-containing reactants include ammonia or hydrazine. In certainembodiments, the first nitrogen-containing reactant is an amine, forexample a C₁₋₁₀ alkyl amine. In certain embodiments, the firstnitrogen-containing reactant is tert-butyl amine.

In some embodiments, the substrate is exposed to a vapor phase flow of asecond nitrogen-containing reactant that is different from said firstnitrogen-containing reactant. The first nitrogen-containing reactant canbe carbon-free with the second nitrogen-containing reactant containingcarbon. In certain embodiments, the volumetric flow ratio of the firstnitrogen-containing reactant to the second nitrogen-containing reactantis between about 1:1 and 10:1, for example between about 1:1 and 4:1. Incertain embodiments, the volumetric flow ratio of the firstnitrogen-containing reactant to the second nitrogen-containing reactantis between about 1:10 and 1:1, for example between about 1:4 and 1:1.

In certain embodiments, the pressure in the reaction chamber is cycledsuch that it is higher during the vapor phase flow of thesilicon-containing reactant. For example, the pressure in the reactionchamber can be cycled between a first pressure and a second pressure,the first pressure being between about 5 and 50 Torr and the secondpressure between about 1 and 5 Torr.

In certain embodiments, the substrate is continuously exposed to thevapor phase flow of the first nitrogen-containing reactant through themethod. In certain embodiments, the substrate is periodically exposed tothe vapor phase flow of the first nitrogen-containing reactant.

In certain embodiments, low temperature processes are provided, with thetemperature maintained at no more than about 400° C. or lower, forexample no more than 375° C., 350° C. or 325° C. In certain embodiments,the stress of the silicon nitride material can be tuned. For example, asilicon nitride material having a stress between about −4 GPa and −2 GPcan be deposited. In another example, a silicon nitride material havinga stress between about −2 GPa and 1 GPa can be deposited. The siliconnitride material can be halogen-free. In certain embodiments, thesilicon nitride material is halogen- and carbon-free.

One aspect of the invention relates to a method of forming a siliconnitride material on a substrate, including providing the substrate in areaction chamber; exposing the substrate to a TSA reactant in the vaporphase so that the TSA reactant is adsorbed onto the surface of thesubstrate; exposing the substrate to a nitrogen-containing reactant inthe vapor phase so that the nitrogen-containing reactant is adsorbedonto the surface of the substrate; and igniting a plasma while thenitrogen-containing reactant is present in the vapor phase. Thesubstrate surface can include a raised or recessed feature. Thesubstrate can include one or more of a metal such as copper, adielectric material such as silicon oxide, or agermanium-antimony-tellurium (GST) alloy, for example. In someembodiments, the nitrogen-containing reactant is a carbon-free nitrogencontaining reactant such as ammonia or hydrazine. In some embodiments,the nitrogen-containing reactant is a carbon-containing reactant. Insome embodiments, the nitrogen-containing reactant is a mixture of acarbon-containing reactant and carbon-free nitrogen-containing reactant.The substrate temperature can be, for example, between about 300° C. andabout 450° C., or between about 300° C. and about 400° C. In someembodiments, the temperature is less than 400° C. RF power can bebetween about 0.15-0.5 W/cm² in some embodiments.

Another aspect relates to an apparatus for depositing a silicon nitridefilm. The apparatus can include a reaction chamber; a source ofactivation energy to form the silicon nitride film; a reactant inlet;and a controller. The controller can include instructions for flowingfirst and second nitrogen-containing reactants into the reaction chamberduring a deposition cycle; periodically flowing a halogen-freesilicon-containing reactant into the reaction chamber during thedeposition cycle; and periodically igniting a plasma in the reactionchamber when the flow of the silicon-containing reactant has ceased andwhile the first and second nitrogen-containing reactants are present inthe vapor phase in the reaction chamber.

These and other features and advantages of the present invention will bedescribed in more detail below with reference to the associateddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a temporal progression of exemplary phases in a CFDprocess.

FIG. 2-4 show example process flows for making a SiN film.

FIG. 5 depicts an example of a CFD processing station.

FIG. 6 depicts an example of a schematic view of a multi-stationprocessing tool.

FIG. 7 shows an I-V curve for a SiN film deposited using TSA/ammoniasystem.

FIG. 8 shows bottom and side step coverage of SiN films deposited usingTSA/ammonia systems for various feature aspect ratios.

DETAILED DESCRIPTION Overview

The present disclosure relates to formation of SiN films, particularlyon semiconductor substrates. Methods described herein include ways ofcontrolling the carbon content in SiN films, particularly forminglow-carbon content SiN films, as well as conformal film deposition (CFD)methods of forming SiN films.

DEFINITIONS

As used herein, the following definitions shall apply unless otherwiseindicated.

A “silicon-containing reactant” is a reagent, single or mixture ofreagents, used to make a SiN material, where the reagent contains atleast one silicon compound. The silicon compound can be, for example, asilane, a halosilane or an aminosilane. A silane contains hydrogenand/or carbon groups, but does not contain a halogen. Examples ofsilanes are silane (SiH₄), disilane (Si₂H₆), and organo silanes such asmethylsilane, ethylsilane, isopropylsilane, t-butylsilane,dimethylsilane, diethylsilane, di-t-butylsilane, allylsilane,sec-butylsilane, thexylsilane, isoamylsilane, t-butyldisilane,di-t-butyldisilane, and the like. A halosilane contains at least onehalogen group and may or may not contain hydrogens and/or carbon groups.Examples of halosilanes are iodosilanes, bromosilanes, chlorosilanes andfluorosilanes. Although halosilanes, particularly fluorosilanes, mayform reactive halide species that can etch silicon materials, in certainembodiments described herein, the silicon-containing reactant is notpresent when a plasma is struck. Specific chlorosilanes aretetrachlorosilane (SiCl₄), trichlorosilane (HSiCl₃), dichlorosilane(H₂SiCl₂), monochlorosilane (ClSiH₃), chloroallylsilane,chloromethylsilane, dichloromethylsilane, chlorodimethylsilane,chloroethylsilane, t-butylchlorosilane, di-t-butylchlorosilane,chloroisopropylsilane, chloro-sec-butylsilane,t-butyldimethylchlorosilane, thexyldimethylchlorosilane, and the like.An aminosilane includes at least one nitrogen atom bonded to a siliconatom, but may also contain hydrogens, oxygens, halogens and carbons.Examples of aminosilanes are mono-, di-, tri- and tetra-aminosilane(H₃Si(NH₂)₄, H₂Si(NH₂)₂, HSi(NH₂)₃ and Si(NH₂)₄, respectively), as wellas substituted mono-, di-, tri- and tetra-aminosilanes, for example,t-butylaminosilane, methylaminosilane, tert-butylsilanamine,bis(tertiarybutylamino)silane (SiH₂(NHC(CH₃)₃)₂ (BTBAS), tert-butylsilylcarbamate, SiH(CH₃)—(N(CH₃)₂)₂, SiHCl—(N(CH₃)₂)₂, (Si(CH₃)₂NH)₃ andthe like. A further example of an aminosilane is trisilylamine(N(SiH₃)).

A “nitrogen-containing reactant” contains at least one nitrogen, forexample, ammonia, hydrazine, amines (amines bearing carbon) such asmethylamine, dimethylamine, ethylamine, isopropylamine, t-butylamine,di-t-butylamine, cyclopropylamine, sec-butylamine, cyclobutylamine,isoamylamine, 2-methylbutan-2-amine, trimethylamine, diisopropylamine,diethylisopropylamine, di-t-butylhydrazine, as well as aromaticcontaining amines such as anilines, pyridines, and benzylamines. Aminesmay be primary, secondary, tertiary or quaternary (for example,tetraalkylammonium compounds). A nitrogen-containing reactant cancontain heteroatoms other than nitrogen, for example, hydroxylamine,t-butyloxycarbonyl amine and N-t-butyl hydroxylamine arenitrogen-containing reactants.

“Plasma” refers to a plasma ignited in a reaction chamber or remotelyand brought into the reaction chamber. Plasmas can include the reactantsdescribed herein and may include other agents, for example, a carriergas, or reactive species such as hydrogen gas. The reactants and otheragents may be present in a reaction chamber when a plasma is struck, ora remote plasma may be flowed into a chamber where the reactants arepresent and/or the reactants and/or carrier gas may be ignited into aplasma remotely and brought into the reaction chamber. A “plasma” ismeant to include any plasma known to be technologically feasible,including inductively-coupled plasmas and microwave surface waveplasmas. One of ordinary skill in the art would appreciate thatadvancements in technology will occur, and thus as yet developed plasmagenerating techniques are contemplated to be within the scope of theinvention.

“Thermally removable group” refers to a moiety, on either or both of thenitrogen-containing reactant and the silicon-containing reactant, thatbreaks down into volatile components at between about 200° C. and about550° C. Described herein are non-limiting examples such as secondary andtertiary carbon group, which undergo elimination reactions in thistemperature range. One of ordinary skill in the art would recognize thatother groups thermally decompose as described by other mechanisms, forexample, a t-butyloxycarbonyl (t-BOC or “BOC”) group thermallydecomposes via both an elimination mechanism where the t-butyl portionof the group forms isobutylene, but also the decomposition forms carbondioxide. Thus a thermally removable group is not limited to a particularmechanism or combination of mechanisms. As long as the group breaks downunder the specified temperature range to produce at least one volatilecomponent, then it qualifies as a thermally decomposable group. Forexample, under a given set of conditions, t-butylethylamine will undergothermal decomposition of the t-butyl group to form isobutylene while theethyl group remains, and thus isobutylene and ethylamine are theproducts of the thermal decomposition. One of ordinary skill in the artwould recognize that the volatility of a component depends, in part, onthe reaction conditions under which the component is generated. Forexample, isobutylene may be volatile and be removed from a reactionchamber under the conditions of heating and low press because it doesnot react with the adsorbed reactants, while, for example, ammonia,although generally a volatile compound, undergoes reaction with asilicon-containing reactant adsorbed on the surface of a substrate.

Methods

Described herein are methods of making SiN films. In particularembodiments SiN films are made using plasma-activated conformal filmdeposition (CFD). In some embodiments, SiN films are deposited using anaminosilane silicon-containing reactant. In some embodiments, SiN filmsare deposited using non-halogen aminosilanes. In some embodiments, SiNfilms are deposited using trisilylamine.

In some embodiments, SiN films are deposited using a carbon-freenitrogen-containing reactant. In some embodiments, SiN films aredeposited using ammonia. In some embodiments, SiN films are depositedusing a mixture of a carbon-free compound nitrogen-containing reactantand a carbon-containing nitrogen-containing reactant.

In some embodiments, halogen-free conformal SiN films are deposited. Insome embodiments, halogen- and carbon-free conformal SiN films aredeposited. In some embodiments, halogen-free conformal SiN films havinga tuned stress are deposited. In some embodiments, conformal SiN filmsare deposited at temperatures less than about 400° C. Each of theseaspects is described in more detail below.

In certain embodiments, CFD is used to deposit the SiN films, althoughmethods described herein are not limited to CFD. Other suitable methodsinclude ALD, PEALD, CVD, PECVD, and plasma enhanced cyclic chemicalvapor deposition (PECCVD). Methods for forming films using CFD aredescribed in U.S. patent application Ser. No. 13/084,399, filed on Apr.11, 2011, and which is incorporated by reference herein for allpurposes. For context, a short description of CFD is provided.

Manufacture of semiconductor devices typically involves depositing oneor more thin films on a non-planar substrate in an integratedfabrication process. In some aspects of the integrated process it may beuseful to deposit conformal thin films. For example, a silicon nitridefilm may be deposited on top of an elevated gate stack to act as aspacer layer for protecting lightly-doped source and drain regions fromsubsequent ion implantation processes.

In spacer layer deposition processes, chemical vapor deposition (CVD)processes may be used to form a silicon nitride film on the non-planarsubstrate, which is then anisotropically etched to form the spacerstructure. However, as a distance between gate stacks decreases, masstransport limitations of CVD gas phase reactions may cause“bread-loafing” deposition effects. Such effects typically exhibitthicker deposition at top surfaces of gate stacks and thinner depositionat the bottom corners of gate stacks. Further, because some die may haveregions of differing device density, mass transport effects across thewafer surface may result in within-die and within-wafer film thicknessvariation. These thickness variations may result in over-etching of someregions and under-etching of other regions. This may degrade deviceperformance and/or die yield.

Some approaches to addressing these issues involve atomic layerdeposition (ALD). In contrast with a CVD process, where thermallyactivated gas phase reactions are used to deposit films, ALD processesuse surface-mediated deposition reactions to deposit films on alayer-by-layer basis. In one example ALD process, a substrate surface,including a population of surface active sites, is exposed to a gasphase distribution of a first reactant (A). Some molecules of reactant Amay form a condensed phase atop the substrate surface, includingchemisorbed species and physisorbed molecules of reactant A. The reactoris then evacuated to remove gas phase and physisorbed reactant A so thatonly chemisorbed species remain. A second film reactant (B) is thenintroduced to the reactor so that some molecules of reactant B adsorb tothe substrate surface. Thermal energy provided to the substrateactivates surface reactions between adsorbed molecules of reactants Aand B, forming a film layer. Finally, the reactor is evacuated to removereaction by-products and unreacted reactant B, ending the ALD cycle.Additional ALD cycles may be included to build film thickness. Plasma,or other energetic means, may be used in conjunction with heating, or asalternatives to heating the substrate in order to drive the reactionbetween reactant A and B.

Depending on the exposure time of the reactant dosing steps and thesticking coefficients of the reactants, each ALD cycle may deposit afilm layer of, in one example, between one-half and three angstromsthick. Thus, ALD processes may be time consuming when depositing filmsmore than a few nanometers thick. Further, some reactants may have longexposure times to deposit a conformal film, which may also reduce waferthroughput time.

Conformal films may also be deposited on planar substrates. For example,antireflective layers for lithographic patterning applications may beformed from planar stacks comprising alternating film types. Suchantireflective layers may be approximately 100 to 1000 angstroms thick,making ALD processes less attractive than CVD processes. However, suchanti-reflective layers may also have a lower tolerance for within-waferthickness variation than many CVD processes may provide. For example, a600-angstrom thick antireflective layer may tolerate a thickness rangeof less than 3 angstroms.

Various embodiments described herein include CFD to deposit SiN films.Generally, CFD does not rely on complete purges of one or more reactantsprior to reaction to form SiN. For example, there may be one or morereactants present in the vapor phase when a plasma (or other activationenergy) is struck. Accordingly, one or more of the process stepsdescribed in the ALD process may be shortened or eliminated in anexample CFD process. Further, in some embodiments, plasma activation ofdeposition reactions may result in lower deposition temperatures thanthermally-activated reactions, potentially reducing the thermal budgetof an integrated process.

FIG. 1, shows a temporal progression of exemplary phases in a CFDprocess, 100, for various process parameters, for example, inert gasflow, reactant A, reactant B and when a plasma is struck. In FIG. 1, twodeposition cycles 110A and 110B are shown. One of ordinary skill in theart would appreciate that any suitable number of deposition cycles maybe included in a CFD process to deposit a desired film thickness.Example CFD process parameters include, but are not limited to, flowrates for inert and reactant species, plasma power and frequency,substrate temperature, and process station pressure.

The concept of a CFD “cycle” is relevant to the discussion of variousembodiments herein. Generally a cycle is the minimum set of operationsrequired to perform a surface deposition reaction one time. The resultof one cycle is production of at least a partial film layer on asubstrate surface. Typically, a CFD cycle will include only those stepsnecessary to deliver and adsorb each reactant to the substrate surface,and then react those adsorbed reactants to form the partial layer offilm. The cycle may include certain ancillary steps such as sweeping oneof the reactants or byproducts and/or treating the partial film asdeposited. Generally, a cycle contains only one instance of a uniquesequence of operations. As an example, a cycle may include the followingoperations: (i) delivery/adsorption of reactant A, (ii)delivery/adsorption of reactant B, (iii) sweep B out of the reactionchamber, and (iv) apply plasma to drive a surface reaction of A and B toform the partial film layer on the surface.

Referring to FIG. 1, an inert gas is flowed during all phases of process100. At reactant A exposure phase, 120A, reactant A is supplied at acontrolled flow rate to a process station to saturate exposed surfacesof a substrate. Reactant A may be any suitable deposition reactant, forexample, a nitrogen-containing reactant. In the embodiment shown in FIG.1, reactant A flows continuously throughout deposition cycles 110A and110B. Unlike a typical ALD process, where film precursor (reactant)exposures are separated to prevent gas phase reaction, reactants A and Bmay be allowed to mingle in the gas phase of some embodiments of a CFDprocess. Continuously supplying reactant A to the process station mayreduce or eliminate a reactant A flow rate turn-on and stabilizationtime compared to an ALD process where reactant A is first turned on,then stabilized and exposed to the substrate, then turned off, andfinally removed from a reactor. While the embodiment shown in FIG. 1depicts reactant A exposure phase 120A as having a constant flow rate,it will be appreciated that any suitable flow of reactant A, including avariable flow, may be employed within the scope of the presentdisclosure. In some embodiments, reactant A exposure phase 120A may havea duration that exceeds a substrate surface saturation time for reactantA. For example, the embodiment of FIG. 1 includes a reactant Apost-saturation exposure time 130 in reactant A exposure phase 120A.Optionally, reactant A exposure phase 120A may include a controlled flowrate of an inert gas. Example inert gases include, but are not limitedto, nitrogen, argon, and helium. The inert gas may be provided to assistwith pressure and/or temperature control of the process station,evaporation of a liquid reactant, more rapid delivery of the reactantand/or as a sweep gas for removing process gases from the processstation and/or process station plumbing.

At reactant B exposure phase 140A of the embodiment shown in FIG. 1,reactant B is supplied at a controlled flow rate to the process stationto saturate the exposed substrate surface. In this example, reactant Bcan be a nitrogen-containing reactant, for example. While the embodimentof FIG. 1 depicts reactant B exposure phase 140A as having a constantflow rate, it will be appreciated that any suitable flow of reactant B,including a variable flow, may be employed within the scope of thepresent disclosure. Further, it will be appreciated that reactant Bexposure phase 140A may have any suitable duration. In some embodiments,reactant B exposure phase 140A may have a duration exceeding a substratesurface saturation time for reactant B. For example, the embodimentshown in FIG. 1 depicts a reactant B post-saturation exposure time 150included in reactant B exposure phase 140A.

In some embodiments, surface adsorbed B species may exist asdiscontinuous islands on the substrate surface, making it difficult toachieve surface saturation of reactant B. Various surface conditions maydelay nucleation and saturation of reactant B on the substrate surface.For example, ligands released on adsorption of reactants A and/or B mayblock some surface active sites, preventing further adsorption ofreactant B. Accordingly, in some embodiments, continuous adlayers ofreactant B may be provided by modulating a flow of and/or discretelypulsing reactant B into the process station during reactant B exposurephase 140A. This may provide extra time for surface adsorption anddesorption processes while conserving reactant B compared to a constantflow scenario. Additionally, or alternatively, in some embodiments, oneor more sweep phases may be included between consecutive exposures ofreactant B.

Prior to activation of the plasma, gas phase reactant B may be removedfrom the process station in sweep phase 160A in some embodiments.Sweeping the process station may avoid gas phase reactions wherereactant B is unstable to plasma activation or where unwanted speciesmight be formed. Further, sweeping the process station may removesurface adsorbed ligands that may otherwise remain and contaminate thefilm. Example sweep gases may include, but are not limited to, argon,helium, and nitrogen. In the embodiment shown in FIG. 1, sweep gas forsweep phase 160A is supplied by the continuous inert gas stream. In someembodiments, sweep phase 160A may include one or more evacuationsubphases for evacuating the process station. Alternatively, it will beappreciated that sweep phase 160A may be omitted in some embodiments.

Sweep phase 160A may have any suitable duration. In some embodiments,increasing a flow rate of a one or more sweep gases may decrease theduration of sweep phase 160A. For example, a sweep gas flow rate may beadjusted according to various reactant thermodynamic characteristicsand/or geometric characteristics of the process station and/or processstation plumbing for modifying the duration of sweep phase 160A. In onenon-limiting example, the duration of a sweep phase may be optimized byadjustment of the sweep gas flow rate. This may reduce deposition cycletime, which may improve substrate throughput.

At plasma activation phase 180A of the embodiment shown in FIG. 1,plasma energy is provided to activate surface reactions between surfaceadsorbed reactants A and B. For example, the plasma may directly orindirectly activate gas phase molecules of reactant A to form reactant Aradicals. These radicals may then interact with surface adsorbedreactant B, resulting in film-forming surface reactions. Plasmaactivation phase 180A concludes deposition cycle 110A, which in theembodiment of FIG. 1 is followed by deposition cycle 110B, commencingwith reactant A exposure phase 120B, and continuing with B exposurephase 140B, sweep phase 160B and plasma activation phase 180B.

In some embodiments, the plasma ignited in plasma activation phase 180Amay be formed directly above the substrate surface. This may provide agreater plasma density and enhance a surface reaction rate betweenreactants A and B. For example, plasmas for CFD processes may begenerated by applying a radio frequency (RF) field to a low-pressure gasusing two capacitively coupled plates. Any suitable gas may be used toform the plasma. In this example, the inert gas such as argon or heliumis used along with reactant A, a nitrogen-containing reactant, to formthe plasma. Ionization of the gas between the plates by the RF fieldignites the plasma, creating free electrons in the plasma dischargeregion. These electrons are accelerated by the RF field and may collidewith gas phase reactant molecules. Collision of these electrons withreactant molecules may form radical species that participate in thedeposition process. It will be appreciated that the RF field may becoupled via any suitable electrodes. Non-limiting examples of electrodesinclude process gas distribution showerheads and substrate supportpedestals. It will be appreciated that plasmas for CFD processes may beformed by one or more suitable methods other than capacitive coupling ofan RF field to a gas.

Plasma activation phase 180A may have any suitable duration. In someembodiments, plasma activation phase 180A may have a duration thatexceeds a time for plasma-activated radicals to interact with allexposed substrate surfaces and adsorbates, forming a continuous filmatop the substrate surface. For example, the embodiment shown in FIG. 1includes a plasma post-saturation exposure time 190 in plasma activationphase 180A.

In some embodiments, extending a plasma exposure time and/or providing aplurality of plasma exposure phases may provide a post-reactiontreatment of bulk and/or near-surface portions of the deposited film. Inone embodiment, decreasing surface contamination may prepare the surfacefor adsorption of reactant A. For example, a silicon nitride film formedfrom reaction of a silicon-containing reactant and a nitrogen-containingreactant may have a surface that may resist adsorption of subsequentreactants. Treating the silicon nitride surface with a plasma may createhydrogen bonds for facilitating subsequent adsorption and reactionevents. The SiN films described herein can be exposed toother-than-plasma treatments.

In some embodiments, a treatment other than a plasma treatment isemployed to modify the properties the as deposited film. Such treatmentsinclude electromagnetic radiation treatments, thermal treatments (e.g.,anneals or high temperature pulses), and the like. Any of thesetreatments may be performed alone or in combination with anothertreatment, including a plasma treatment. Any such treatment can beemployed as a substitute for any of the above-described plasmatreatments. In a specific embodiment, the treatment involves exposingthe film to ultraviolet radiation. As described below, in a specificembodiment, the method involves the application of UV-radiation to afilm in situ (i.e., during formation of the film) or post deposition ofthe film. Such treatment serves to reduce or eliminate defect structureand provide improved electrical performance.

In certain specific embodiments, a UV treatment can be coupled with aplasma treatment. These two operations can be performed concurrently orsequentially. In the sequential option, the UV operation optionallytakes place first. In the concurrent option, the two treatments may beprovided from separate sources (e.g., an RF power source for the plasmaand a lamp for the UV) or from a single source such as a helium plasmathat produces UV radiation as a byproduct.

In some embodiments, film properties, such as film stress, dielectricconstant, refractive index, etch rate may be adjusted by varying plasmaparameters.

While many examples discussed herein include two reactants (A and B), itwill be appreciated that any suitable number of reactants may beemployed within the scope of the present disclosure. In someembodiments, a single reactant and an inert gas used to supply plasmaenergy for a surface reaction can be used. Alternatively, someembodiments may use multiple reactants to deposit a film. For example,in some embodiments, a silicon nitride film may be formed by reaction ofa silicon-containing reactant and one or more of a nitrogen-containingreactant, or one or more silicon-containing reactants and a singlenitrogen-containing reactant, or more than one of both thesilicon-containing reactant and the nitrogen-containing reactant.

In certain embodiments, a halogen-free silicon-containing reactant isemployed to deposit a halogen-free SiN film. FIG. 1 provides an exampleof a process that may be used to deposit a halogen-free SiN film, withtrisilylamine (TSA) is employed as a reactant B in the example ofFIG. 1. While FIG. 1 provides an example of a process to deposit a SiNfilm, various modifications possible. For example, in some embodiments,flows of reactant A and B may be alternated with optional purge gases inbetween the flows. In another example, reactant A can be asilicon-containing reactant, with reactant B a nitrogen-containingreactant. In some embodiments, a plasma may be struck only when the flowof the silicon-containing reactant is stopped.

In certain embodiments, a halogen-free silicon-containing reactant isemployed. In a particular example, trisilylamine (TSA) is employed as asilicon-containing reactant. TSA is an isolatable, stable aminosilane.

FIGS. 2 and 3 depict examples of process flows 200 and 300 that use TSA.First turning to FIG. 2, a substrate is provided to a chamber, see 205.The substrate can be any appropriate substrate on which a SiN film isdesired. For example, the substrate can be a partially fabricatedintegrated circuit, flash memory or phase-change memory substrate. Thesubstrate can be provided as a bare substrate, e.g., a bare siliconsubstrate, or with one or more layers deposited thereon. The surface onwhich the SiN film is to be deposited can be or include, for example,silicon, polysilicon, copper, tituanium, tungsten, silicon dioxide, or agermanium-antimony-tellurium (GST) alloy. In some embodiments, thesurface includes one or more raised or recessed features. The one ormore raised features can have aspect ratios of 2:1-10:1, for example.The substrate is exposed to TSA, see 210. In some embodiments, operation210 is a non-plasma operation. The reactor can be pressurized, in someembodiments, to a first pressure between about 5 and 50 Torr, forexample. In a particular embodiment, pressure is about 20 Torr duringoperation 210. Pressures outside this range may be used according to thedesired embodiment. TSA is adsorbed on the substrate surface. After thedesired amount of TSA is adsorbed on the surface, the flow of TSA isstopped (not shown). The substrate is then exposed to one or morenitrogen-containing reactants, see 215. A plasma is struck while thenitrogen-containing reactant is present in the vapor phase, see 220,thus forming a halogen-free SiN film on the substrate. In someembodiments, the pressure in the reactor is cycled such that it is lowerduring operations 215 and/or 220 than operation 210. For example, thepressure during these operations can be between about 1 and 5 Torr, forexample 2 Torr. The flow of the nitrogen-containing reactant(s) can bestopped (not shown) after 220 in some embodiments.

In one embodiment, the TSA not adsorbed to the surface of the substrateis swept out of the chamber by the flow of the inert gas and/ornitrogen-containing reactant(s) prior to striking the plasma. In anotherembodiment, a purge may be used to remove vapor phase silicon-containingreactant. In some embodiments, a purge may be used after 220 as well.

One or more iterations of 210-220 can be performed to build up a SiNlayer. In one embodiment, these operations are repeated to form aconformal layer on the substrate between about 1 nm and about 100 nmthick. In another embodiment, between about 5 nm and about 50 nm thick.In another embodiment, between about 5 nm and about 30 nm thick.

In one embodiment, using any of the methods described herein, thesubstrate is heated to between about 50° C. and about 550° C., or moreparticularly from about 300° C. to about 450° C., for example about 350°C. or 400° C. In one embodiment, the wafer is heated throughout thedeposition, in other embodiments the wafer is heated periodically duringthe deposition or after the deposition steps as an anneal.

FIG. 3 depicts a process flow, 300, outlining aspects of an embodimentof the method. A substrate is provided to the chamber, see 305. A flowof one or more nitrogen-containing reactants is established andcontinued throughout 300, see 310. The substrate is periodically exposedto TSA, see 315. Also, periodically, a plasma is struck, see 320, butonly when the TSA reactant flow has ceased. In one embodiment, the TSAnot adsorbed to the surface of the substrate is swept out of the chamberby the flow of an inert gas and/or nitrogen-containing reactant(s). Inanother embodiment, a purge may be used. After the plasma treatment, thecycle is complete. Operations 310-320 may be repeated a number of timesto build up a layer of desired thickness.

FIG. 4 depicts a process flow 400, outlining aspects of an embodiment ofa method. A substrate is provided to the chamber, see 405. A carrierflow is established, see 410. The substrate is exposed to anitrogen-containing reactant, see 415. The substrate is exposed to asilicon-containing reactant, see 420. A plasma is ignited after the flowof the silicon-containing reactant is ceased, see 425. This reactionforms SiN. One or more iterations of 410-425 are performed to build alayer of desired thickness. In this method, 415 and 420 are notnecessarily done in the order presented. The nitrogen-containingreactant flow may or may not be continuous.

Various additional operations may be incorporated into any of theabove-described processes. For example, in some embodiments, after allor part of the SiN film is formed to a desired thickness, the SiN filmcan be exposed to a hydrogen plasma. This can remove carbon content, ifany, from the SiN film. In one embodiment, the hydrogen plasma isgenerated using hydrogen (H₂) and a carrier gas such as nitrogen, heliumor argon. Other hydrogen containing gases, or active hydrogen atomsproduced by a remote plasma source, may be used to treat the depositedfilm. Further, in some embodiments, the carbon content of the film maybe tuned to any suitable concentration by varying one or more of thenumber of treatment pulses and their duration, the intensity of thetreatment plasma, the substrate temperature, and the treatment gascomposition.

Halogen-Free Silicon-Containing Reactants

While FIGS. 2-4 provide example process flows for deposition of SiNusing TSA, in some embodiments, other SiN films are deposited usingnon-halogen aminosilanes may be used instead of or in addition to TSA.The TSA or other aminosilane may be unsubstituted or optionallysubstituted with any non-halogen substituent. In some embodiments,unsubstituted TSA (SiH₃)₃N is used. In some embodiments, TSA substitutedwith one or more carbon-containing substituents may be used. Examples ofcarbon-containing substituents include alkyl, alkenyl, alkynyl, andother organic groups.

The use of a halogen-free silicon-containing reactant can beadvantageous for deposition on certain substrates that are especiallysusceptible to etching and/or corrosion by halide byproducts of thedeposition process. These include metal substrates such as copper,tungsten, titanium substrates and GST alloys. For example, tungsten anda choride byproduct may react to form volatile tungsten hexachloride,removing the underlying tungsten. In another example, a chloride gas maycorrode copper.

The use of a halogen-free silicon-containing reactant can also be usefulfor low temperature (e.g., 400° C. and less than 400° C.) reactions.This is because halogen-containing silicon reactants can produce solidbyproducts, such as NH₄Cl that cannot be removed as voltatile byproductsin low temperature reactions. TSA can be used for low temperaturereactions as it more reactive at the surface than, for example,dichlorosilane (DCS).

In some embodiments, TSA may be used with any suitablenitrogen-containing reactant. In one embodiment, the nitrogen-containingreactant is selected from the group consisting of ammonia, a hydrazine,an amine and mixtures thereof. In one embodiment, thenitrogen-containing reactant includes a C₁₋₁₀ alkyl amine or a mixtureof C₁₋₁₀ alkyl amines. In one embodiment, the C₁₋₁₀ alkyl amine is aprimary alkyl amine or a secondary alkyl amine. In one embodiment, theC₁₋₁₀ alkyl amine is a primary alkyl amine. In one embodiment, the C₁₋₁₀alkyl amine is according to formula I:

wherein each of R¹, R² and R³ is, independent of the others, H or C₁₋₃alkyl; or two of R¹, R² and R³, together with the carbon atom to whichthey are attached form a C₃₋₇ cycloalkyl and the other of R¹, R² and R³is H or C₁₋₃ alkyl. In one embodiment, the C₁₋₁₀ alkyl amine has asecondary or tertiary carbon attached directly to the nitrogen. In oneembodiment, the C₁₋₁₀ alkyl amine is selected from the group consistingof isopropylamine, cyclopropylamine, sec-butylamine, tert-butyl amine,cyclobutylamine, isoamylamine, 2-methylbutan-2-amine and thexylamine(2,3-dimethylbutan-2-amine). In one embodiment, in the C₁₋₁₀ alkyl amineof Formula I, each of R¹, R² and R³ is C₁₋₃ alkyl. In one embodiment,the C₁₋₁₀ alkyl amine is tert-butyl amine (TBA). TBA can be particularlyuseful for the reasons described.

In some embodiments, the SiN film produced has an undesirable carboncontent. This in-film carbon may result in electrical leakage and mayrender the film unusable for some dielectric barrier applications.Carbon content can vary, but in some embodiments approximately 10%carbon (by weight) can be considered too high. Methods described hereinaddress unwanted carbon in SiN films. Methods described herein produceSiN films with less than 2% carbon, in one embodiment less than 1%carbon, in yet another embodiment less than 0.5% carbon. In someembodiments, the reduction in carbon residue is readily observable inFTIR spectra, although other analytical methods are known to one ofordinary skill in the art that can measure carbon content in theseranges.

In some embodiments, the nitrogen-containing reactant can contain athermally removable group. A thermally removable group is a group thatbreaks down into volatile components at between about 200° C. and about550° C. For example, secondary and particularly tertiary carbon groupscan undergo elimination reactions in this temperature range. In aparticular example, t-butyl groups break down to form isobutylene inthis temperature range. For example, t-butylamine, when heated,undergoes an elimination reaction to form isobutylene and ammonia. Asanother example, t-butoxycarbonyl groups (t-BOC) groups also thermallydecompose, for example at about 150° C., to form isobutylene, carbondioxide and theradical to which the t-BOC group was attached. Forexample, t-butylcarbamate thermally decomposes to give isobutyleneammonia and carbon dioxide.

The substrate can be heated to between about 200° C. and about 550° C.so that such groups decompose and release their carbon content and thusreduce the carbon content of the SiN film. The reactants are adsorbedonto the substrate, a plasma is used to convert the reactants to a SiNmaterial. Remaining carbon groups can be removed by heating thesubstrate. The heating can be performed during the entire deposition orperiodically to decompose the thermally removable groups. In oneembodiment, the substrate is heated to between about 200° C. and about550° C., in another embodiment between about 350° C. and about 550° C.,in another embodiment between about 450° C. and about 550° C., and inanother embodiment, between about 450° C. and about 500° C. In oneembodiment, for example where TBA is used, the SiN film can be heated tobetween about 450° C. and about 500° C., for between about 1 second andabout 30 seconds, or between about 1 second and about 20 seconds, orbetween about 1 second and about 10 seconds. Although any particularthermally removable group will breakdown at a certain temperaturethreshold, a higher temperature may be used to increase the rate ofdecomposition and/or as an anneal to improve the properties of the SiNfilm.

As described above, the thermally removable group may include asecondary or tertiary carbon functionality. Either or both of thesilicon-containing reactant and the nitrogen-containing reactant caninclude one or more of the same or different thermally removable groups.In one embodiment, the thermally removable group is according to FormulaII:

wherein each of R¹, R² and R³ is, independent of the others, H or C₁₋₃alkyl; or two of R¹, R² and R³, together with the carbon atom to whichthey are attached form a C₃₋₇ cycloalkyl and the other of R¹, R² and R³is H or C₁₋₃ alkyl; and where each of said thermally removable group,when part of the nitrogen-containing reactant, is attached to a nitrogenor an oxygen of the nitrogen-containing reactant, and, when part of thesilicon-containing reactant, is attached to a silicon or a nitrogen oran oxygen of the silicon-containing reactant. In one embodiment, each ofR¹, R² and R³ is, independent of the others, C₁₋₃ alkyl. In oneembodiment, the thermally removable group is a t-butyl group.

Carbon-Free Nitrogen Containing Reactants

In some embodiments, the nitrogen-containing reactant is a carbon-freenitrogen-containing reactant. Examples include ammonia and hydrazine.For example, in some embodiments, TSA and ammonia are used as thesilicon-containing reactant and nitrogen-containing reactant,respectively, for the deposition of SiN.

In some embodiments, for example, a carbon-free nitrogen-containingreactant is used to deposit the SiN film of a SiO₂/SiN/SiO₂ (also knownas an ONO stack) for flash memory. The deposited film can be halogen-and carbon-free without even trace amounts of halogen or carbon present(unless from a contaminant source such as humans or an insufficientlyclean after a previous process in the deposition tool).

Tuning Stress and Wet Etch Rate

In some embodiments, the nitrogen-containing reactant(s) can be chosento tune the stress and/or wet etch rate of the deposited SiN film. Forexample, ammonia or other carbon-free nitrogen-containing reactant canbe used to deposit tensile films having a high wet etch rate.

In another example, TBA or other carbon-containing nitrogen-containingreactant can be used to deposit etch resistant, compressive films.

In some embodiments, two nitrogen-containing reactants can be used totune the stress of the desired film. For example, a carbon-containingnitrogen-containing reactant (e.g., TBA) and a carbon-freenitrogen-containing reactant (e.g., ammonia) can be used to deposit aSiN film having a desired stress and wet etch rate. In some embodiments,these nitrogen-containing reactants can be used with TSA to deposit achlorine-free SiN film having a desired stress and wet etch rate.

In this manner, SiN films having stress ranging from −4 GPa(compressive) to 2 GPa (tensile) can be achieved. For example, in someembodiments, compressive SiN films having a stress between about −4 GPaand about −2 GPa can be achieved using a nitrogen-containing reactantflow of pure TBA (or other carbon-containing nitrogen-containingreactant). In some embodiments, tensile SiN having a stress betweenabout 1 GPa and about 2 GPa can be achieved using a nitrogen-containingreactant flow of pure ammonia (or other carbon-free nitrogen-containingreactant). In some embodiments, a SiN film having a stress between about−2 GPa and 1 GPa can be achieved using a mixture of TBA (or othercarbon-containing nitrogen-containing reactant) and ammonia (or othercarbon-free nitrogen-containing reactant).

The stress values achievable using pure TBA (or other carbon-containingnitrogen-containing reactant), pure ammonia (or other carbon-freenitrogen-containing reactant) and mixtures of these can vary accordingto the particular embodiment and other process conditions including RFpower and plasma duration during plasma phases of the processesdescribed herein. Longer and higher power plasma can make a SiN filmmore compressive. In some embodiments, a SiN film deposited using TSAand only a carbon-free nitrogen-containing reactant(s) (e.g., ammoniaand/or hydrazine) can be tuned to have a stress of anywhere fromslightly compressive, e.g., −0.5 GPa, to a tensile stress of up to 2 GPaby appropriately modulating the RF power.

In some embodiments, for example, a tensile (1-2 GPa) SiN film can bedeposited using TSA and a carbon-free nitrogen-containing reactant witha HFRF power of about 0.15 W/cm², with a slightly compressive SiN filmdeposited using TSA and a carbon-free nitrogen-containing reactant witha HFRF power close 1 W/cm². (RF powers are expressed in W/area of thesubstrate, e.g., a 300 mm wafer has an area of approximately 706 cm².)The films can be made more compressive by adding TBA or othercarbon-containing nitrogen-containing reactant. In some cases, it can bedifficult to form tensile films using TBA as a relatively high RF poweris used to decompose the t-butyl group of the TBA molecule. Accordingly,it may be useful to use a carbon-free nitrogen containing reactant suchas ammonia or hydrazine to achieve a tensile film. The RF plasmas areHF-only plasmas, though in some other embodiments, some LF power can beadded.

The achievable ranges of wet etch using TSA and carbon-free reactantsystems are also greater than conventional processes. For example wetetch rate ratio to thermal oxide (WERR) for SiN films deposited usingTSA/ammonia can be about 2.0 for low HFRF power as described above.Increasing HFRF power to about 1 W/cm² or greater can lower the WERR toabout 0.5. This compares to WERR for DCS/TBA systems, which can rangefrom about 0.1 to 1.0.

Deposition at Low Temperature

As noted above, TSA can be used for low temperature reactions as it morereactive at the surface than, for example, dichlorosilane. In addition,in some embodiments, carbon-free nitrogen containing reactants allowdeposition of high quality SiN films at lower temperatures than TBA orother nitrogen-containing reactants. For example, a DCS/TBA systembegins to shows degraded sidewall deposition at 400° C. and below due topoor decomposition kinetics of the t-butyl group in the TBA molecule.

In some embodiments, SiN deposition using a halogen-free aminosilane anda carbon-free nitrogen-containing reactant can provide high quality SiNfilms at temperatures significantly lower than achievable with DCS/TBAand similar systems. For example, TSA/ammonia provide high qualitydeposition at 350° C., as well as at 400° C. or 450° C. Accordingly, insome embodiments, TSA can be used with one or more carbon-freenitrogen-containing reactants to at temperatures ranging from 50° C. to450° C., or from 50° C. to 400° C., or from 50° C. to 350° C.

Conformal Films

According to various embodiments, the processes described herein candeposit SiN films that are highly conformal to the substrate surface onwhich they are deposited. In some embodiments, step coverage is at least90%. For the purposes of this description, “step coverage” is defined asa ratio of two thicknesses of the deposited film, with bottom stepcoverage being the ratio: thickness at the bottom of thefeature/thickness at the top of the feature, and side step coveragebeing the ratio: thickness on a sidewall of the feature/thickness at thetop of the feature.

Apparatus

Another aspect of the invention is an apparatus configured to accomplishthe methods described herein. A suitable apparatus includes hardware foraccomplishing the process operations and a system controller havinginstructions for controlling process operations in accordance with thepresent invention.

It will be appreciated that any suitable process station may be employedwith one or more of the embodiments described above. For example, FIG. 5schematically shows a CFD process station 1300. For simplicity, CFDprocess station 1300 is depicted as a standalone process station havinga process chamber body 1302 for maintaining a low-pressure environment.However, it will be appreciated that a plurality of CFD process stations1300 may be included in a common low-pressure process tool environment.While the embodiment depicted in FIG. 5 shows one process station, itwill be appreciated that, in some embodiments, a plurality of processstations may be included in a processing tool. For example, FIG. 6depicts an embodiment of a multi-station processing tool 2400. Further,it will be appreciated that, in some embodiments, one or more hardwareparameters of CFD process station 1300, including those discussed indetail below, may be adjusted programmatically by one or more computercontrollers.

A CFD process station 1300 fluidly communicates with reactant deliverysystem 1301 for delivering process gases to a distribution showerhead1306. Reactant delivery system 1301 includes a mixing vessel 1304 forblending and/or conditioning process gases for delivery to showerhead1306. One or more mixing vessel inlet valves 1320 may controlintroduction of process gases to mixing vessel 1304.

Some reactants may be stored in liquid form prior to vaporization at andsubsequent delivery to the process station. For example, the apparatusof FIG. 5 includes a vaporization point 1303 for vaporizing liquidreactant to be supplied to mixing vessel 1304. In some embodiments,vaporization point 1303 may be a heated vaporizer. The saturatedreactant vapor produced from such vaporizers may condense in downstreamdelivery piping. Exposure of incompatible gases to the condensedreactant may create small particles. These small particles may clogpiping, impede valve operation, contaminate substrates, etc. Someapproaches to addressing these issues involve sweeping and/or evacuatingthe delivery piping to remove residual reactant. However, sweeping thedelivery piping may increase process station cycle time, degradingprocess station throughput. Thus, in some embodiments, delivery pipingdownstream of vaporization point 1303 is heat traced. In some examples,mixing vessel 1304 is also heat traced. In one non-limiting example,piping downstream of vaporization point 1303 has an increasingtemperature profile extending from approximately 100° C. toapproximately 150° C. at mixing vessel 1304.

In some embodiments, reactant liquid is vaporized at a liquid injector.For example, a liquid injector may inject pulses of a liquid reactantinto a carrier gas stream upstream of the mixing vessel. In oneembodiment, a liquid injector vaporizes reactant by flashing the liquidfrom a higher pressure to a lower pressure. In another embodiment, aliquid injector atomizes the liquid into dispersed microdroplets thatare subsequently vaporized in a heated delivery pipe. It will beappreciated that smaller droplets may vaporize faster than largerdroplets, reducing a delay between liquid injection and completevaporization. Faster vaporization may reduce a length of pipingdownstream from vaporization point 1303. In one embodiment, a liquidinjector is mounted directly to mixing vessel 1304. In anotherembodiment, a liquid injector is mounted directly to showerhead 1306.

In some embodiments, a liquid flow controller upstream of vaporizationpoint 1303 is provided for controlling a mass flow of liquid forvaporization and delivery to process station 1300. In one example, theliquid flow controller (LFC) includes a thermal mass flow meter (MFM)located downstream of the LFC. A plunger valve of the LFC is adjustedresponsive to feedback control signals provided by aproportional-integral-derivative (PID) controller in electricalcommunication with the MFM. However, it may take one second or more tostabilize liquid flow using feedback control. This may extend a time fordosing a liquid reactant. Thus, in some embodiments, the LFC isdynamically switched between a feedback control mode and a directcontrol mode. In some embodiments, the LFC is dynamically switched froma feedback control mode to a direct control mode by disabling a sensetube of the LFC and the PID controller.

Showerhead 1306 distributes process gases toward substrate 1312. In theembodiment shown in FIG. 5, substrate 1312 is located beneath showerhead1306, and is shown resting on a pedestal 1308. It will be appreciatedthat showerhead 1306 may have any suitable shape, and may have anysuitable number and arrangement of ports for distributing processesgases to substrate 1312.

In some embodiments, a microvolume 1307 is located beneath showerhead1306. Performing a CFD process in a microvolume rather than in theentire volume of a process station may reduce reactant exposure andsweep times, may reduce times for altering CFD process conditions (e.g.,pressure, temperature, etc.), may limit an exposure of process stationrobotics to process gases, etc. Example microvolume sizes include, butare not limited to, volumes between 0.1 liter and 2 liters.

In some embodiments, pedestal 1308 may be raised or lowered to exposesubstrate 1312 to microvolume 1307 and/or to vary a volume ofmicrovolume 1307. For example, in a substrate transfer phase, pedestal1308 is lowered to allow substrate 1312 to be loaded onto pedestal 1308.During a CFD process phase, pedestal 1308 is raised to positionsubstrate 1312 within microvolume 1307. In some embodiments, microvolume1307 completely encloses substrate 1312 as well as a portion of pedestal1308 to create a region of high flow impedance during a CFD process.

Optionally, pedestal 1308 may be lowered and/or raised during portionsthe CFD process to modulate process pressure, reactant concentration,etc., within microvolume 1307. In one embodiment where process chamberbody 1302 remains at a base pressure during the CFD process, loweringpedestal 1308 allows microvolume 1307 to be evacuated. Example ratios ofmicrovolume to process chamber volume include, but are not limited to,volume ratios between 1:500 and 1:10. It will be appreciated that, insome embodiments, pedestal height may be adjusted programmatically by asuitable computer controller.

In another embodiment, adjusting a height of pedestal 1308 allows aplasma density to be varied during plasma activation and/or treatmentcycles included in the CFD process. At the conclusion of the CFD processphase, pedestal 1308 is lowered during another substrate transfer phaseto allow removal of substrate 1312 from pedestal 1308.

While the example microvolume variations described herein refer to aheight-adjustable pedestal, it will be appreciated that, in someembodiments, a position of showerhead 1306 may be adjusted relative topedestal 1308 to vary a volume of microvolume 1307. Further, it will beappreciated that a vertical position of pedestal 1308 and/or showerhead1306 may be varied by any suitable mechanism. One of ordinary skill inthe art would appreciate that such mechanism would include, for example,hydraulics, pneumatics, spring mechanisms, solenoids and the like. Insome embodiments, pedestal 1308 may include a rotational mechanism, forexample along an axis perpendicular to the surface of the substrate, forrotating an orientation of substrate 1312. It will be appreciated that,in some embodiments, one or more of these example adjustments may beperformed programmatically by one or more suitable computer controllers.

Returning to the embodiment shown in FIG. 5, showerhead 1306 andpedestal 1308 electrically communicate with RF power supply 1314 andmatching network 1316 for powering a plasma. In some embodiments, theplasma energy is controlled by controlling one or more of a processstation pressure, a gas concentration, an RF source power, an RF sourcefrequency, and a plasma power pulse timing. For example, RF power supply1314 and matching network 1316 may be operated at any suitable power toform a plasma having a desired composition of radical species. Examplesof suitable powers include, but are not limited to, powers between 100 Wand 5000 W. Likewise, RF power supply 1314 may provide RF power of anysuitable frequency. In some embodiments, RF power supply 1314 may beconfigured to control high- and low-frequency RF power sourcesindependently of one another. Example low-frequency RF frequencies mayinclude, but are not limited to, frequencies between 50 kHz and 500 kHz.Example high-frequency RF frequencies may include, but are not limitedto, frequencies between 1.8 MHz and 2.45 GHz. It will be appreciatedthat any suitable parameters may be modulated discretely or continuouslyto provide plasma energy for the surface reactions. In one non-limitingexample, the plasma power may be intermittently pulsed to reduce ionbombardment with the substrate surface relative to continuously poweredplasmas.

In some embodiments, the plasma is monitored in-situ by one or moreplasma monitors. In one embodiment, plasma power is monitored by one ormore voltage, current sensors (e.g., VI probes). In another embodiment,plasma density and/or process gas concentration is measured by one ormore optical emission spectroscopy sensors (OES). In some embodiments,one or more plasma parameters are programmatically adjusted based onmeasurements from such in-situ plasma monitors. For example, an OESsensor may be used in a feedback loop for providing programmatic controlof plasma power. It will be appreciated that, in some embodiments, othermonitors may be used to monitor the plasma and other processcharacteristics. Such monitors include, but are not limited to, infrared(IR) monitors, acoustic monitors, and pressure transducers.

In some embodiments, the plasma is controlled via input/output control(IOC) sequencing instructions. For example, the instructions for settingplasma conditions for a plasma process phase may be included in acorresponding plasma activation recipe phase of a CFD process recipe. Insome embodiments, process recipe phases may be sequentially arranged, sothat all instructions for a CFD process phase are executed concurrentlywith that process phase. It will be appreciated that some aspects ofplasma generation may have well-characterized transient and/orstabilization times that may prolong a plasma process phase. Put anotherway, such time delays may be predictable. Such time delays may include atime to strike the plasma and a time to stabilize the plasma at theindicted power setting.

In some embodiments, pedestal 1308 may be temperature controlled viaheater 1310. Further, in some embodiments, pressure control for CFDprocess station 1300 may be provided by butterfly valve 1318. As shownin FIG. 5, butterfly valve 1318 throttles a vacuum provided by adownstream vacuum pump (not shown). However, in some embodiments,pressure control of process station 1300 may also be adjusted by varyinga flow rate of one or more gases introduced to CFD process station 1300.

As described above, one or more process stations may be included in amulti-station processing tool. FIG. 6 shows a schematic view of amulti-station processing tool, 2400, with an inbound load lock 2402 andan outbound load lock 2404, either or both of which may comprise aremote plasma source. A robot 2406, at atmospheric pressure, isconfigured to move wafers from a cassette loaded through a pod 2408 intoinbound load lock 2402 via an atmospheric port 2410. A wafer is placedby the robot 2406 on a pedestal 2412 in the inbound load lock 2402, theatmospheric port 2410 is closed, and the load lock is pumped down. Wherethe inbound load lock 2402 comprises a remote plasma source, the wafermay be exposed to a remote plasma treatment in the load lock prior tobeing introduced into a processing chamber 2414. Further, the wafer alsomay be heated in the inbound load lock 2402 as well, for example, toremove moisture and adsorbed gases. Next, a chamber transport port 2416to processing chamber 2414 is opened, and another robot (not shown)places the wafer into the reactor on a pedestal of a first station shownin the reactor for processing. While the embodiment depicted in FIG. 6includes load locks, it will be appreciated that, in some embodiments,direct entry of a wafer into a process station may be provided.

The depicted processing chamber 2414 comprises four process stations,numbered from 1 to 4 in the embodiment shown in FIG. 6. Each station hasa heated pedestal (shown at 2418 for station 1), and gas line inlets. Itwill be appreciated that in some embodiments, each process station mayhave different or multiple purposes. For example, in some embodiments, aprocess station may be switchable between a CFD and PECVD process mode.Additionally or alternatively, in some embodiments, processing chamber2414 may include one or more matched pairs of CFD and PECVD processstations. While the depicted processing chamber 2414 comprises fourstations, it will be understood that a processing chamber according tothe present disclosure may have any suitable number of stations. Forexample, in some embodiments, a processing chamber may have five or morestations, while in other embodiments a processing chamber may have threeor fewer stations.

FIG. 6 also depicts a wafer handling system 2490 for transferring waferswithin processing chamber 2414. In some embodiments, wafer handlingsystem 2490 may transfer wafers between various process stations and/orbetween a process station and a load lock. It will be appreciated thatany suitable wafer handling system may be employed. Non-limitingexamples include wafer carousels and wafer handling robots. FIG. 6 alsodepicts a system controller 2450 employed to control process conditionsand hardware states of process tool 2400. System controller 2450 mayinclude one or more memory devices 2456, one or more mass storagedevices 2454, and one or more processors 2452. Processor 2452 mayinclude a CPU or computer, analog and/or digital input/outputconnections, stepper motor controller boards, etc.

In some embodiments, system controller 2450 controls all of theactivities of process tool 2400. System controller 2450 executes systemcontrol software 2458 stored in mass storage device 2454, loaded intomemory device 2456, and executed on processor 2452. System controlsoftware 2458 may include instructions for controlling the timing,mixture of gases, chamber and/or station pressure, chamber and/orstation temperature, wafer temperature, target power levels, RF powerlevels, substrate pedestal, chuck and/or susceptor position, and otherparameters of a particular process performed by process tool 2400.System control software 2458 may be configured in any suitable way. Forexample, various process tool component subroutines or control objectsmay be written to control operation of the process tool componentsnecessary to carry out various process tool processes. System controlsoftware 2458 may be coded in any suitable computer readable programminglanguage.

In some embodiments, system control software 2458 may includeinput/output control (IOC) sequencing instructions for controlling thevarious parameters described above. For example, each phase of a CFDprocess may include one or more instructions for execution by systemcontroller 2450. The instructions for setting process conditions for aCFD process phase may be included in a corresponding CFD recipe phase.In some embodiments, the CFD recipe phases may be sequentially arranged,so that all instructions for a CFD process phase are executedconcurrently with that process phase.

Other computer software and/or programs stored on mass storage device2454 and/or memory device 2456 associated with system controller 2450may be employed in some embodiments. Examples of programs or sections ofprograms for this purpose include a substrate positioning program, aprocess gas control program, a pressure control program, a heatercontrol program, and a plasma control program.

A substrate positioning program may include program code for processtool components that are used to load the substrate onto pedestal 2418and to control the spacing between the substrate and other parts ofprocess tool 2400.

A process gas control program may include code for controlling gascomposition and flow rates and optionally for flowing gas into one ormore process stations prior to deposition in order to stabilize thepressure in the process station. A pressure control program may includecode for controlling the pressure in the process station by regulating,for example, a throttle valve in the exhaust system of the processstation, a gas flow into the process station, etc.

A heater control program may include code for controlling the current toa heating unit that is used to heat the substrate. Alternatively, theheater control program may control delivery of a heat transfer gas (suchas helium) to the substrate.

A plasma control program may include code for setting RF power levelsapplied to the process electrodes in one or more process stations.

In some embodiments, there may be a user interface associated withsystem controller 2450. The user interface may include a display screen,graphical software displays of the apparatus and/or process conditions,and user input devices such as pointing devices, keyboards, touchscreens, microphones, etc.

In some embodiments, parameters adjusted by system controller 2450 mayrelate to process conditions. Non-limiting examples include process gascomposition and flow rates, temperature, pressure, plasma conditions(such as RF bias power levels), pressure, temperature, etc. Theseparameters may be provided to the user in the form of a recipe, whichmay be entered utilizing the user interface.

Signals for monitoring the process may be provided by analog and/ordigital input connections of system controller 2450 from various processtool sensors. The signals for controlling the process may be output onthe analog and digital output connections of process tool 2400.Non-limiting examples of process tool sensors that may be monitoredinclude mass flow controllers, pressure sensors (such as manometers),thermocouples, etc. Appropriately programmed feedback and controlalgorithms may be used with data from these sensors to maintain processconditions.

System controller 2450 may provide program instructions for implementingthe above-described deposition processes. The program instructions maycontrol a variety of process parameters, such as DC power level, RF biaspower level, pressure, temperature, etc. The instructions may controlthe parameters to operate in-situ deposition of film stacks according tovarious embodiments described herein.

The system controller will typically include one or more memory devicesand one or more processors configured to execute the instructions sothat the apparatus will perform a method in accordance with the presentinvention. Machine-readable media containing instructions forcontrolling process operations in accordance with the present inventionmay be coupled to the system controller.

Patterning Method/Apparatus:

The apparatus/process described herein may be used in conjunction withlithographic patterning tools or processes, for example, for thefabrication or manufacture of semiconductor devices, displays, LEDs,photovoltaic panels and the like. Typically, though not necessarily,such tools/processes will be used or conducted together in a commonfabrication facility. Lithographic patterning of a film typicallycomprises some or all of the following steps, each step enabled with anumber of possible tools: (1) application of photoresist on a workpiece,i.e., substrate, using a spin-on or spray-on tool; (2) curing ofphotoresist using a hot plate or furnace or UV curing tool; (3) exposingthe photoresist to visible or UV or x-ray light with a tool such as awafer stepper; (4) developing the resist so as to selectively removeresist and thereby pattern it using a tool such as a wet bench; (5)transferring the resist pattern into an underlying film or workpiece byusing a dry or plasma-assisted etching tool; and (6) removing the resistusing a tool such as an RF or microwave plasma resist stripper. In oneembodiment, a SiN film is formed using a method as described herein. TheSiN film is used, for example, for one of the purposes described herein.Further, the method includes one or more steps (1)-(6) described above.

EXAMPLES

The invention is further understood by reference to the followingexamples, which are intended to be purely exemplary. The presentinvention is not limited in scope by the exemplified embodiments, whichare intended as illustrations of single aspects of the invention only.Any methods that are functionally equivalent are within the scope of theinvention. Various modifications of the invention in addition to thosedescribed herein will become apparent to those skilled in the art fromthe foregoing description and accompanying figures. Moreover, suchmodifications fall within the scope of the appended claims.

Example 1

Table 1 includes a number of reaction partners, and temperature andpressure parameters that may be used to make SiN films in accordancewith the embodiments described herein.

Nitrogen- Containing RF Power Process Silicon-Containing Reactant(s)Density ID Reactant (% are vol. %) Temp (° C.) (W/cm²) A TSA NH₃ 50-5500.15-3   B TSA NH₃ 50-450 0.15-0.5  C TSA NH₃ 300-400  0.15-0.5  D TSANH₃ 300-400  1-3 E TSA 75% NH₃/ 50-550 0.15-3   25% TBA G TSA 50% NH3/50-550 1-3 50% TBA H TSA 25% NH3/ 50-550 1-3 75% TBA I TSA TBA 400-550 1-3

Process A uses TSA as a silicon-containing reactant with ammonia as thenitrogen-containing reactant. Temperatures can range from 50° C. toabout 550° C. according to the requirements of the substrate beingprocessed. RF power can range from about 0.15 W/cm² to about 3 W/cm² totune the stress as described above.

Process B is a specific example of process A, using TSA and ammonia at alower temperature of between about 50° C. and 450° C., depending onthermal budget concerns, to deposit a tensile SiN film. Substrateshaving copper films for example, may be processed at less than about400° C. to prevent alteration of the grain structure of the copper. GSTalloys, for example, may be processed at temperatures around 350°C.-375° C. As described above, TSA and ammonia can be used to providehigh quality films having high step coverage at these lower temperaturesat reasonable deposition rates. RF power is relatively low to achieve atensile film.

Process C is another specific example of process A, using TSA andammonia at a lower temperature of between about 300° C. and 400° C.,depending on thermal budget concerns, to deposit a tensile SiN film.Temperatures in this range may be useful to deposit SiN films onsubstrates including copper, GST alloys, and other thermally sensitivematerials, while maintaining a higher deposition rate.

Process D is another specific example of process A, and is similar toprocess C except using a higher RF power to deposit a more compressivefilm.

Processes E-H are examples of processes that use mixtures of ammonia andTBA as nitrogen-containing reactants to tune the stress and wet etchrate of the deposited SiN film. In one example, Process E could be usedwith a high RF level such as that of Process D, with the presence of TBAmaking the film even more compressive.

Process I is an example of a process using TSA and TBA assilicon-containing and nitrogen-containing reactants, respectively.Process I may be used, for example, to deposit a compressivehalogen-free SiN film.

In the above process examples, carbon-free nitrogen-containing reactantssuch as hydrazine may be used instead of or in addition to ammonia.Other carbon-containing reactants as described above may be used insteadof or in addition to TBA.

Example 2

A 300 mm wafer is placed into vacuum chamber. The wafer is supportedwithin the chamber on an aluminum pedestal which is heated throughoutthe procedure. For example, the pedestal is heated at a constanttemperature that is between about 50° C. and about 550° C. Trisilylamine(TSA) is introduced into the reactor as a vapor phase flow at betweenabout 0.25 slm and about 5 slm (standard liters per minute) for betweenabout 1 second and about 30 seconds to adsorb TSA onto the surface ofthe wafer. After the TSA flow is ceased, the inert gas flow in thereactor purges the remaining vapor phase TSA and any byproducts. Then,an ammonia vapor phase flow is established in the reactor at betweenabout 1 slm and about 10 slm for between about 1 second and about 30seconds. A plasma, for example 13.56 MHz at 150 W power, is ignitedabove the wafer for between about 1 second and about 15 seconds. Theinert gas flow in the reactor purges the remaining vapor phase ammoniaand any byproducts. The TSA flow, inert gas purge, ammonia flow, plasmaand inert gas purge are repeated to deposit a SiN film of desiredthickness. Each cycle as described deposits between about 0.5 Å andabout 1.5 Å of a SiN film.

Alternatively, 1-5 slm of TBA can be used in addition to or instead ofthe ammonia.

In another alternative, in a CFD run, the ammonia flow (and/or TBA flow)is run continuously. In these runs, the same conditions as describedabove are used, except the ammonia flow is established first andmaintained. The TSA flow is introduced into the reactor at the same rateand time as described above, followed by an inert gas purge as describedabove. The plasma is ignited as described above, followed by an inertgas purge as described above. The TSA flow, inert gas purge, plasmaignition and inert gas purge are repeated to deposit a SiN film ofdesired thickness. Each cycle as described deposits between about 0.5 Åand about 1.5 Å of a SiN film.

Example 3

A process as described in Example 2 was used to deposit SiN films usingTSA and ammonia at 450° C. FIG. 7 shows an I-V curve for a depositedfilm. Notably, the SiN film does not break down for applied fields of upabout 22 MV/cm. FIG. 8 shows bottom and side step coverage for variousfeature aspect ratios.

Processes were used to deposit SiN films with the following systems:DCS/TBA, TSA/TBA and TSA/ammonia. The refractive index for each film wasDCS/TBA: 1.83, TSA/TBA: 1.83 and TSA/ammonia: 1.90.

Although the foregoing has been described in some detail for purposes ofclarity of understanding, it will be apparent that certain changes andmodifications may be practiced within the scope of the appended claims.It should be noted that there are many alternative ways of implementingthe processes, systems and apparatus described. Accordingly, thedescribed embodiments are to be considered as illustrative and notrestrictive.

These amendments to the claims replace all prior versions of claims inthe application:
 1. An apparatus for depositing a silicon nitride filmon a semiconductor wafer, the apparatus comprising: (a) a reactionchamber; (b) a source of activation energy to form the silicon nitridefilm; (c) a reactant inlet; and (d) a controller comprising instructionsfor: flowing a first nitrogen-containing reactant into the reactionchamber during a deposition cycle; periodically flowing asilicon-containing reactant into the reaction chamber during thedeposition cycle; periodically igniting a plasma in the reaction chamberwhen the flow of the silicon-containing reactant has ceased and whilethe first nitrogen-containing reactant is present in the vapor phase inthe reaction chamber; and cycling the pressure in the reaction chambersuch that it is higher during the flow of the silicon-containingreactant than when the flow of the silicon-containing reactant hasceased.
 2. The apparatus of claim 1, wherein the plasma is an RF plasmahaving a power between 0.15 W/cm² and 3 W/cm².
 3. The apparatus of claim2, wherein the plasma has a power between 0.15 W/cm² and 1 W/cm².
 4. Theapparatus of claim 1, wherein the plasma is an HF-only RF plasma.
 5. Theapparatus of claim 1, wherein the first nitrogen-containing reactant isflowed into the reaction chamber under conditions such that it willadsorb onto the surface of a substrate in the reaction chamber.
 6. Theapparatus of claim 5, wherein the silicon-containing reactant is flowedinto the reaction chamber under conditions such that it will adsorb ontothe surface of the substrate in the reaction chamber.
 7. The apparatusof claim 1, wherein the pressure in the reaction chamber is cycledbetween a first pressure and a second pressure, the first pressure beingbetween about 5 and 50 Torr and the second pressure between about 1 and5 Torr.
 8. The apparatus of claim 1, wherein the firstnitrogen-containing reactant is flowed throughout the deposition cycle.9. The apparatus of claim 1, wherein the first nitrogen-containingreactant is flowed periodically during the deposition cycle.
 10. Theapparatus of claim 1, wherein the controller further comprisesinstructions for: periodically flowing a second nitrogen-containingreactant into the reaction chamber during the deposition cycle, thesecond nitrogen-containing reactant being different than the firstnitrogen-containing reactant.
 11. The apparatus of claim 10, wherein thevolumetric flow ratio of the first nitrogen-containing reactant to thesecond nitrogen-containing reactant is between about 1:1 and 10:1. 12.The apparatus of claim 10, wherein the volumetric flow ratio of thefirst nitrogen-containing reactant to the second nitrogen-containingreactant is between about 1:10 and 1:1.
 13. The apparatus of claim 1,wherein the controller further comprises instructions for: maintainingthe substrate temperature at less than about 400° C.
 14. The apparatusof claim 13, wherein the substrate temperature is maintained at lessthan about 350° C.
 15. The apparatus of claim 1, wherein the siliconnitride material deposited during the deposition cycle has a stressbetween about −4 GPa and −2 GPa.
 16. The apparatus of claim 1, whereinthe silicon nitride material deposited during the deposition cycle has astress between about −2 GPa and 1 GPa.
 17. The apparatus of claim 1,wherein the silicon nitride material deposited during the depositioncycle conforms to the surface of the substrate including any raised orrecessed features of the substrate.
 18. The apparatus of claim 1,wherein the source of activation energy is a plasma generator which isoperated by the controller to periodically ignite the plasma in thereaction chamber.
 19. The apparatus of claim 18, wherein the plasmagenerator comprises induction coils and/or a microwave source.
 20. Asystem comprising the apparatus of claim 1 and a stepper.